The present invention relates to a computer network system for allowing-computers interconnected by a network to interchange data and, more particularly, to a data send confirmation system in which a computer sends a data frame to a receiving computer and determines, on receiving a receive response frame from the receiving computer, that the data successfully reached the receiving computer.
Generally, in a computer network system, several ten to several hundred computers are interconnected by a network and send data asynchronously. It is likely with this kind of system that data sent from the computers conflict on the network or that the receiving computer discards received data due to an insufficient capacity of a receive buffer thereof. In the light of this, it has been customary to cause the receiving computer to return a receive response frame to the sending computer when it has received data correctly. However, the sending computer does not always obtain the receive response immediately since data sent from a great number of sending computers may conflict on the network. For this reason, the sending computer awaits the receive response from the receiving computer for a predetermined period of time given by the system. When the sending computer does not receive the receive response within the predetermined period of time, it again sends the same data to the receiving computer. Further, when the sending computer does not receive the receive response even after repeating the resending operation a predetermined number of times also given by the system, it executes error processing by determining that data transmission has failed. In the event that the sending computer cannot receive the receive response frame, it is a common practice to change the whole system, i.e., to change the number of times that data is to be resent by changing the firmware of each computer or to replace the receive buffer of each computer with a receive buffer having a greater capacity.
However, the conventional computer network system described above has some problems left unsolved, as follows. To begin with, assume that a great number of computers send data to a single computer asynchronously, and that the amount of the data exceeds the processing ability of the receiving computer. Then, the receiving computer simply discards the data due to the insufficient capacity of the receive buffer thereof and cannot return a receive response frame to any of the sending computers. This often occurs in, among other things, a local area network (LAN) whose data transfer rate is high. Specifically, in a LAN, it often occurs that a sending computer cannot obtain a receive response frame from a receiving computer even after resending data a predetermined number of times, resulting in a transmission failure. Another problem with the conventional system is that changing the firmware or replacing the receive buffer computer by computer requires a considerable number of steps and considerable time.